1. Field of the Invention
The present invention relates to an agricultural implement having a plurality of soil packer units which are each positioned ahead of a respective, independent harrow assembly.
2. Description of the Prior Art
Compaction of soil around newly planted seed has long been known to substantially increase crop yield. In the past, soil compaction has sometimes been provided by a number of relatively heavy packing wheels mounted on a cultivator, but unfortunately the packing wheels may cause a substantial amount of stress to be imposed on frame members of the cultivator, and the wheels may also present problems during transport. Certain cultivators have springs to apply force to the packer wheels, but uneven depth control of the cultivator may occur when the weight of the cultivator is less than the forces imposed on the packer wheels.
In recent times, increased interest has been directed toward the concept of soil compaction by means of a series of coil packers coupled to the trailing ends of harrow assemblies. Examples of these types of harrow packer units are shown in U.S. Pat. No. 4,418,762 and Canadian Pat. Nos. 838,417, 871,991, 1,081,021, 1,099,566, and 1,212,569. The coil packer creates a herringbone pattern on the ground which, according to some, is useful for reducing wind and water erosion.
However, certain problems have been observed in connection with the herringbone pattern left in the soil after use of a harrow packer unit. In particular, water uptake by the soil is decreased once the sidewalls of the herringbone packer tracks become hard and crusted, and evaporation losses are increased upon formation of puddles in the tracks. Existing soil moisture may be readily lost due to capillary action within the crusted, packed soil of the tracks which is directly exposed to the atmosphere. Also, the wave-like herringbone pattern increases the total exposed surface area of the field, which causes a corresponding increase in total evaporation losses. Moreover, water runoff is more likely to occur in packed grooves than might occur, for instance, in loose soil.
Other problems that have been observed with regard to harrow packer units include the tendency for the coil packers to reintroduce weeds into the ground that have previously been uprooted during airseeding or during harrowing, thereby encouraging the weeds to continue to grow and compete with the crop. In addition, harrow packer units tend to leave finely crushed soil on the top surface of the ground where it is susceptible to erosion by wind and water.
In some harrow packer units, coil packers are arranged in staggered disposition relative to the normal direction of travel of the implement. In this manner, the width of each coil packer can be increased in an attempt to eliminate missed areas of the ground not subjected to the forces of the coil. However, during relatively sharp turns, some areas of the ground may be left untouched due to the large distance between the coil packers and the axis of turning movement of the implement. Also, such construction increases the cost of the coil packers in proportion to the increased width of the same.
Another problem associated with harrow packer units is due to the relatively complex and expensive mechanism that is often provided for folding the unit into and out of an orientation for transport. In these devices, arms supporting the harrow assemblies are fixed to a transversely extending structural frame member which is selectively pivotable about an axis parallel to its longitudinal axis for raising the unit toward a folded orientation. However, the relatively heavy coils are pivotally coupled by means of an elongated hitch to the trailing ends of the harrow support arms, and therefore relatively stiff structural members and large hydraulic piston and cylinder assemblies are needed for developing sufficient torque to overcome the moment presented by the packer coils and raising the arms toward a vertical orientation. In addition, the coil packers of the folded unit, being supported solely on one side of the harrow by the now overlying pivotal connection, are free to sway and thus present a somewhat unstable arrangement during transport of the unit.
Furthermore, unfolding of the aforementioned harrow packing units requires skill and closely timed operator coordination since the unit must be advanced slowly at a creep speed as the packers are lowered to the ground. Other problems which are encountered in harrow packer units of this type include the tendency of the packers and harrow sections to bind during turns while the unit is in its folded, transport orientation which may lead to serious damage to the tines.